Gas tank in or out?

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I have to do some repair work (MIG) to the passenger side quarter panel of my Mustang. I have always removed gas tanks and batterys from cars and bikes before welding anything. I watched a show on Discovery and they were doing similar work with the gas tank in the car. Am I being too cautious?
Reply:Do you like living?  It might not always be necessary depending on the condition of the gas tank and connections but you will never wake up dead if you remove the gas tank first. Personally, I only pull batteries if I working in the engine compartment. Disconnecting them is a good idea for any welding job
Reply:Had the same question when I 1st MIGged on my car. After spending weeks of research eventually decided that removing tank too cumbersome since I'm only welding at front.BUT I was very cautious - removed battery, covered all gas lines under car close to weld spot with some fire retardant cloth + clamped ground as close to weld spot as posible + fire extinguishers close by + 30 to 45 mins. fire watch after finished.Read somewhere on the net that it's actually better to completely fill your tank with gas coz it expels the fumes in the tank - the guy claims that it's the fumes that cause an explosion and not the gas itself. Does make some sense but follow his at your own discretion.
Reply:The guy at or local muffler shop welds exhaust pipes all day long, less than a foot away from the tank. The family owned business has been around for over 50 years. I doubt that he has ever taken out a tank to weld on the exhaust.Bruce
Reply:I've never welded on a gas tank, but a buddy from the navy has and said that atleast with them diesels to fill em full and purge witha  bottle of inert. Given this, all my experience with heavy equipment and the like I just disconnect the battery and cover lines and hoses, wires and anything else that could cause a problem.  Otherwise, keep a fire extinguisher nearby and best to weld with a spot man.  My advice is on jobs on the car take it easy.  Take it slow and dont put too much heat in there.  Inother words make shorter welds, spread them out and just dont let things under the hood or elsewhere get too hot and dont sweat it.  I've never pulled a battery out of a car except one time to weld a battery box back together that had corroded.  I've even welded on equipment, tractors and such without disconnecting the batt, and in a case of a small crane, never even shut off the motor!   Hope this helpsCHRIS
Reply:I would never consider what I see on Discovery Channel as either a good or safe way to do things. There are so many things done wrong (welding wise) on that channel, from a safety and technical standpoint, that it is a shame.Many of those guys just close their eyes when they tack weld something. I'm sure you will get some people to tell you that is ok also.Yeah some people get away with it. Look at it this way, if you don't get away with it you will never know.   TAKE THE DARN GAS TANK OUT   Be safe. Move the gas tank out in the open while doing the welding so there is no chance a stray spark will set any fumes on fire.Hobbiest hack
Reply:Well dave a wise ole boy once said "this here seperates the men from the boys"   If a fellow comes to you and says,  Hey bubba I need this here crack welded on my car.  You look at it and you say ok thats like 10 mins of work.  Thats disconnecting/reconnecting the batt, draggin out your leads, thats grinding the surface area and puttin in a lil bevel for good penetration, thats welding the joint and finishin with a grinder or paint or whatever you might find fit,  hopefully nothing but maybe a wire brush and chippin hammer.  So you see a job that takes 10 mins.  For ten mins you can tell this fellow its no charge but to tell all his friends.  Or you can say tell you what half sack a beer would be great.  Alternatively you can see this five minute job and say,  golly gee I think a stray spark might catch the fuel tank on fire so I better pull the fuel tank.  Now I've said it many times but while its not necessary you should disconnect the battery.  So you disconnect the battery.  Then you go after that darn gas tank cause you dont want it to explode.  Funny thing is the lil ******* he doesnt believe in runnin on fume so theres some gas in the tank and subsquently you spill some on the ground below you.  Now I dont know how many gas tanks you've pulled for once reason or another.  I'm no mechanic  but Ive pulled a few and some arent so bad, but some are right mad.  So youve added a minmum of half an hour.  Im betting youve gotta add longer, but for short lets add half an hour.  Now although youve removed the tank you know theres a bit of gas in the fuel lines.  You might not have thought of that now.  So now youve gotta deciede what to do about that or whether its just a risk you gotta take.  But I mind you you started off with an enclosed system, now youve got an open system, and you spilled some gas on the ground too.  I sure do hope that has time to dry.  Now if you decieded not to fuss over them fuel lines, or if you just never thought of it either way, than I reckon you move on to preping that weld and making your weld.  So 10 minutes covers batt disconnect,  draggin out your leads, prep'n the weld, making the weld, doing whatever cleanup on the weld might be needed and removing your tools and reconnecting the batt.Now you have to reinstal that darn fuel tank.  Oh I sure hope a stray spark dint find the opening to that fuel line, or a drip or even that lil spill you made pullin the tank.  Now youve got that gas tank put back in, if it took 30 mins to remove im sureit took atleast 40 to reinstall, but for the sake of the this conversation well say 30 minutes.  So to add this up we have ten minutes in the actual welding.  And for me to do the job thats it.  I can be a cheap skate and tell this fellow min charge and get minimum half hour charge on shop welding.  Therefore Im lookin at charging him about 20 bucks.  Doing it your way though, thers the 10 minutes I charge plus you have to charge him an additional hour!  Thats unbelievable!!  An hour and ten minutes for a 2 minute weld!  At $40/hr thats approximately $46!!!  Sure fire way to never see that customer back again.  He is going to feel really crummie about the rip off he got.  He aint gonna say well you are a lot safer and I dont mind paying it.  He's gonna look at you and go your an idiot!   Then I have to remind you,  why did you pull the tank if your gonna leave the fuel lines and the carburator/ throttle body assembly on the car because you know they have gas in the too.  I am always cautious when I work around a car with the cuttin torch or the welder.  Mig technology is far superior to the old oxy acytelene torch and is a lot safer.  Still we must be ever cautious.  But sometimes I think people take their precautions a wee bit too far.  I agree a lot of what I see on the discovery channel is ridiculous.  Its also what is done out there in the real world hobby welder.  Some things are right.  Some things are wrong.  Some things arent necessarily right or good or to be desired, but theres not a good alternative.  Its kinda like givin guns to cops.  We can say in  perfect world we wouldnt need guns for cops.  Yet were not in a perfect world.  And even if cops who use live fire can cause problems, the results of cops carrying and useing live fire far exceeds the risks and the problems caused by them not.  I dont expect you to appreciate what Im sayin,  but I do expect you take into account that being a hobbyest and being a professional are at too way differnt levels.  You may do what you do cause you like it, but I get paid to do it.  I gotta do it faster, better and safer than the other guy because unlike you if I loose an eye, or a finger or an arm,  thats my trade my friend, and its all over.  I like many of my counterparts come on this forum to help enlighten and give valid instruction and advice to hobbyests and students as well as other professionals in some cases.  Sometimes its best to just let the pro's say what they say and dont discount and argue with them.  I'm one I like constructive critizm but I dont beleive that was your intention.  I guess Im done and Ill get down from my high potium.  Good day and good welding
Reply:I have some experience in welding and gas tanks.  Many years ago, I worked in a fab shop.  They use to weld hitches onto the frames of cars.  (Not legal anymore but 25 years ago we did it all the time).      We built a hitch for a particular car, I believe it was a Chev impala, with a rear gas tank under the truck.  Filler spout was behind the license plate.  There was two of us working on the car.  I was the soon to be first year apprentice,  the other welder was the 3rd year, almost a journeymen welder.       We had the hitch clamped onto the frame and the 3rd year crawled under the car and was laying on his back looking up at the tank, and eying up where he was going to start tacking the hitch to the frame.  While he was checking out his start position, he stuck a rod into the stinger, as he was tightening the rod into the stinger, He spun the head, and the rod, brushed the bottom of the gas tank.  and actually burn't a hole into the tank.  Needless to say, he was on fire, the ground was on fire, and gas was pouring out onto him and the ground.  He plugged the hole with is finger. But was also trying to put the flames out.  He only had the use of one hand at the time, due to when things went haywire. He rolled onto his side and his other arm was underneath.  He was very frantic, trying to put out a fire and plug a hole at the same time.  He finally just held his finger in the hole, and by the time he realized it was the right thing to do, he was covered in dry chem.  the fire was out, so was he, and all we had to do was figure out how to get him out without spilling to much more gas.  All this happened in a matter of seconds.  I was onto him with the extinguisher quite quickly.  He did not receive any burns, due to leather gloves and coat.  But he did require some medical attention for inhalation of dry chem.  What save our butts....... the Gas tank was full.  Had it been on the empty side, I may not be here today to type this.  I all the years of welding around and on cars trucks and tractors. I have never removed a tank.  Still don't even after a scare like that.  I was a we bit sheepish afterwords though.... about a month after the car incident.  A truck driver pulled in with a crack in a diesel tank.  Aluminum.  My boss wanted me to weld it up, and I declined the offer to blow myself up.  He laughed at me, and showed me how to do it, his way.  He placed a pipe nipple into a fitting and filled tank with water until the water ran out of the nipple (which was higher than the top of the tank)  He welded the crack while I stood on the other side of the yard, and plugged my ears waiting for a big boom.  I got paid at the end of the week, after he signed the check, and as far as I know he's retired now and quite happy with life.      Inert gas works, as does steam. My learning was.... always pay attention to where the rod tip is when your stingers loaded.    Packrat.Lincoln 225 AC/DC, Hobart 140 Mig. Oxy/propane Victor torch.(2) Makita 5" angle grinders  one with zip disk, 14" chop saw.  and just about every other tool you can think of. Whoever has the most toys when he die's ..... Wins!
Reply:TxRedneck, you sure know how to ramble on. I'm not sure what your point was about 'constructive criticism'. By the time I got through your long unformatted paragraph my head was spinning.I guess to summarize what you said....Leave it to a pro, they have experience cutting corners just so they can make money and undercut the guy that does worry a little more about safety.If you are not a pro, don't bother offering an opinion on something because the 'pro' know better.Don't worry about what is seen on TV because the general population does works that way. Who cares if it is spreading bad info to 'hobbiest' non professionals. They don't know any better anyway.Quite frankly I don't care how many corners you cut. Doesn't affect me one bit. For all I care you can prop your vehicles up on edge with a single 4x4 piece of lumber and crawl under it. Many of us have seen that picture (from some damn 3rd world country) of the welder under the truck. That saves a lot of time too.I was under the impression that the original poster didn't have any experience in this area and was deserving of a different opinion concerning the safety of welding around gas tanks. Just because YOU get away with it (seems to be standard operating procedure for you) doesn't mean that someone without your years(?) of experience is going to have the same result.Hobbiest hack
Reply:Well if I recall in the original post it talked about welding on a quater panel. I own a auto body shop and have hung more quaters then I want to remember. So for what its worth this is my oponion. Typically we dont remove the fuel tank. We have a hard enough time getting paid by ins co for the operations that are absolutely necessary. The problem arises when you have a vehicle that has a fuel door located in the side of the qtr panel. I dont care if you have not 1 drop of fuel in that tank or the tank is so full its flowing out of the filler neck. Your gonna have fumes( which is where the danger is) coming out of your filler neck. And youll need to plug weld right next to it in that opening for the fuel door. Alot depends on the particular vehicle. But sometimes well remove the filler neck, and plug the opening off, seal it up real well. Then put fire protection over the tank, ie welding blanket, tin, sometimes both, depending on the situation, design of the vehicle etc. Whatever you do, DO NOT Do your plug welds in the fuel door opening area with that filler neck in there. Even if you have a new gas cap, and think its air tight, its just too close. At the very least remove the filler neck, if its removable, and seal it up closer to the tank. If the filler neck cant be removed and you have to weld in that fuel door opening then remove the tank. Thats how a quater panel is installed in most professional bodyshops....   Keep on smashen those cars- show me the money.
Reply:ok dave,So you think your safer?  what about that open fuel line where you disconnected from the fuel tank??  did you stop to consider thats a wee bit more dangerous than the enclosed fuel tank????   And sorry but your idea of being safe really isnt as safe as you think.  My point is that.  And I think that most folks in here are kind of understanding that.   I dont cut corners.  I do the job the best way that makes since.  I do it in a fashion that is safe and to the point.  Wish I could say the same about your methods.
Reply:Txredneck... just what the he$$ do you know about my methods?  I never said I did or did not plug up the gas lines. Maybe I was remiss in mentioning that. Spilling gas on the floor and then welding before its all dried out and the fumes are gone. Guess I didn't mention that either.Txredneck...do it however you want. You don't live near me so I don't give one rats behind how you do it. To tell someone that is not an expert in welding around gas tanks that it is ok to do because you haven't had a problem yet is just totally irresponsible. Since I don't think anyone has mentioned having a BIG fire extinguisher around when you are welding near a gas tank (or any welding for that matter)I guess I'll mention that now too.I would say the original poster has gotten enough feedback that he can make his own informed decision.I wonder what OSHA would say (for you US folks) or your insurance company?Hobbiest hack
Reply:heres my two cents and I might be wrong.I never weld an an automobile without removing the tank first, my reasoning is not because of the danger of sparks igniting fumes so much, of course this is a danger but can usually be avoided with proper preparation. but I have heard and experienced sparks between metal parts that you are welding on becausee of the current flow. Doesent electricity take the easiest way to ground? You could have a spark in or around the tank even if you are welding up front ten feet away from the tank. its probably pretty unlikly and I might be wrong but i wont be dead wrong